Effects Of Acid Precipitation Research Articles

Effects of Methane Fermentation on Spectral Properties of Fulvic Acid Extracted from Peat through Liquid Acid Precipitation

The effects of acid precipitation with different liquid acids on spectral properties of fulvic acid extracted from peat was studied to select the most appropriate liquid acid for the acid precipitation step of the alkali solution acid precipitation method, and the new process mechanism of peat utilization by coupling methane fermentation and extraction of fulvic acid was analyzed. The alkali solution acid precipitation method was adopted to extract fulvic acid from the methane-fermented group and methane-unfermented group. Different liquid acids were used to conduct acid precipitation during the extraction. And then, the characterizations of fulvic acid samples were conducted through Fourier infrared spectroscopy, UV-Vis spectroscopy, and fluorescence spectroscopy. The yield and content of fulvic acid decreased significantly after methane fermentation. During the methane fermentation process, some fulvic acid was consumed and utilized by microorganisms to promote the methane fermentation process, resulting both in the decrease of methyl, hydroxyl, and ether bonds and in the increase of methylene, carbonyl, conjugated double bond, benzene rings, and other groups. The E4/E6 ratio shows that the E4/E6 ratio of fulvic acid was decreased after methane fermentation, and the fermentation consumed the functional group with simpler structure such as aliphatic chain hydrocarbon of fulvic acid while the structure with a higher degree of aromatization and conjugate cannot be consumed. When conducting acid precipitation with different liquid acids, the yield of fulvic acid was the highest through acid precipitation with phosphoric acid. The fulvic acid obtained through acid precipitation with nitric acid has a higher content, more benzene rings, and the highest degree of aromatization.

Minnesota diatomists: The first 150 years

Minnesota boasts over 12,000 lakes, most of glacial origin, three major continental drainage systems (Mississippi River to the Gulf of Mexico, Lake Superior via the other Great Lakes to the Atlantic Ocean, and the Red River of the North via the Nelson River, to Hudson Bay), and a diversity of landforms comprising seven major ecological regions. Such landscape and aquatic variability hosts a high diversity of diatoms, which have been studied for over 150 years. Diatom communities range from saline and eutrophic in the southwest agricultural lands, to oligotrophic and endemic forms in the cold waters of Lake Superior. Early diatom collections were distributed to reknowned diatomists such as C.G. Ehrenberg and H.L. Smith. Other botanists and phycologists, including Tilden, Eddy, and Drouet, were active in Minnesota but only rarely included diatoms in their studies. Interest in Minnesota diatoms increased in the latter half of the 20th century with taxonomic and floristic surveys (e.g., Czarnecki, Koppen, and Kingston) and the inclusion of diatoms in applied research efforts that set the groundwork for understanding post-glacial ecology, effects of Euroamerican settlement, impacts of climate, and the effects of acid precipitation. Important to these latter developments were the efforts of Dr. Herb Wright Jr., who invited several European diatomists (e.g., Florin, Battarbee, and Haworth) to work on paleoecological projects in and near Minnesota. Although not a diatomist per se, Wright's subsequent efforts to promote diatom research included the appointment of Platt Bradbury as a research associate and later John Kingston, Dick Brugam, and Brian Cumming. Students Sheri Fritz, Kate Laird, and Virginia Card completed diatom research for their doctoral degrees. These workers and others have left a legacy that continues to fuel several active labs in Minnesota that have used diatoms to develop water quality standards, assess and restore impaired waters, and understand the impacts of climate, management, and landuse change across the state.

Increasing Ca2+ deposition in the western US: The role of mineral aerosols

Considerable research has focused on the role of industrial emissions in controlling the acidity of precipitation; however, much less research has focused on the role of mineral aerosols emitted from soils. According to data published by the National Atmospheric Deposition Network (NADP), over the past 17 years Ca 2+ deposition has increased over large regions of the US. A trend analysis to determine regions 2+ deposition revealed statistically significant increases in three broad regions within the western half of the country: the inter-mountain west, the midwest, and the northwest. We evaluated potential changes in sources of calcium to the atmosphere including soil erosion, industrial emissions, forest fires, and sea-salt aerosols to determine the cause of rising atmospheric calcium deposition. Based on our evaluation, the most parsimonious explanation for increased Ca 2+ deposition is an increase in mineral aerosol emissions from within the western US. This explanation is corroborated by independent evidence showing increases in the frequency of dust storms and low-visibility days across regions of the western US. Furthermore, our analysis indicates that the increase in mineral aerosol emissions is most likely due to (1) increased aridity and wind transport and (2) increased area and intensity of upwind human activities. Changes in atmospheric dust concentrations can have important ecological implications through the contribution of acid neutralizing capacity to both precipitation and regions of deposition. Thus increased dust emissions have the potential to ameliorate the detrimental effects of acid precipitation on terrestrial ecosystems, though dust may exacerbate the impacts of air quality on human health.

Effects of Acid Precipitation on Agricultural Crops and Forest Trees

Effects of Acid Precipitation on Agricultural Crops and Forest Trees

Testing the MAGIC acid rain model in highly organic, low-conductivity waters using multiple calibrations

Accurate predictions of acid precipitation effects on water resources are important in order to allow a better understanding of various pollution control strategy outcomes. Dynamic geochemical models have been developed to address this need, but have to be tested under a variety of environmental conditions to provide confidence in their predictions. The most commonly used aquatic acidification model in North America and Europe is the model of acidification of groundwater in catchments (MAGIC). Though extensively used, MAGIC has never been tested in catchments with extremely low ionic strength water and high in natural organic acids (NOAs) from wetlands, two conditions which are common in large parts of Canada. We calibrated the model for two catchments located in Nova Scotia, Canada, which had some of the most dilute freshwaters reported in the literature and very high NOA. We also evaluated the variability inherent in calibration data sets by using five separate data sets collected over a 15-year period at the same sites. We show good model simulations for the main cations and anions in catchment waters. However, modeling pH is more difficult in the highly organic waters and requires modification to the acid dissociation constants. Calculated acid neutralization capacity can also be more difficult to model due to the low ion content making small errors more important. In theory, multiple calibrations of a model at a same site should produce identical hindcasts and predictions. In reality, the multiple calibrations produced a series of similar, but not identical outcomes which give a probable range of past values and future outcomes. We feel that this practical approach to validation is a useful addition to the arsenal of model testing tools.

Effects of Acid Precipitation and Aluminum on Carbohydrate Metabolism in Mycorrhizae of Pinus massioniana

Effects of Acid Precipitation and Aluminum on Carbohydrate Metabolism in Mycorrhizae of Pinus massioniana

English

Abstract. Extensive coal mining in the Cheat watershed that started in the early 20 th century has left many streams and parts of the river severely degraded by acid mine drainage. Very little water treatment was conducted until 1977, when the Surface Mining Control and Reclamation Act (SMCRA) was enacted to prevent degradation from water quality from existing mines and funds were created to restore the abandoned mine sites. This was accomplished through bonding and a tax on coal tonnage. Since SMCRA, several once-active sites have been forfeited to the state to pay for the remediation from the bonding program and several of these contribute to the overall problem. The AML fund from the coal tax addresses the pre-law or previous to 1977 sites by funding reclamation on sites that have no legally responsible party. The headwaters that had escaped damage from mining began seeing the effects of acid precipitation in the late 20th century from Midwest coal fired power plants and many streams lost all alkalinity because of poorly buffered soils. Poor water quality from these streams contributed to the degradation of the river. Because of these activities, much of the lower 25 miles of the watershed were without significant aquatic life by the early 1980s. Reclamation started in the watershed in the early 1980s and many projects have been completed. Not all of the projects addressed AMD; however, water quality has steadily improved over this period and some stream segments have shown significant increases in aquatic life in the past few years. This watershed has been the focus of state and federal agencies, watershed and conservation groups, and efforts are ongoing to further improve the water quality. The Cheat hosts a multitude of recreational activities and this makes continued restoration a high priority.

Detection of conspecific alarm cues by juvenile salmonids under neutral and weakly acidic conditions: laboratory and field tests.

A variety of fishes possess damage-released chemical alarm cues, which play a critical role in the detection and avoidance of potential predation threats. Recently, we have demonstrated that the ability of fathead minnows ( Pimephales promelas) and finescale dace ( Phoxinus neogaeus) to detect and respond to conspecific alarm cues is significantly reduced under weakly acidic conditions (pH 6.0). Rainbow trout ( Oncorhynchus mykiss) and brook charr ( Salvelinus fontinalis) possess an analogous alarm cue system. However, it is unknown if the trout alarm cue system is likewise affected by relatively small changes in pH. In addition, previous studies have not verified this phenomenon under natural conditions. We conducted laboratory and field trials to examine the potential effects of acute exposure to weakly acidic (pH 6.0) conditions on the detection and response of conspecific alarm cues by juvenile trout. Our laboratory results demonstrate that while juvenile rainbow trout exhibit significant increases in antipredator behaviour under normal pH conditions (pH 7.0-7.2), they do not respond to the presence of conspecific chemical alarm cues (i.e. response is not different from controls) under weakly acidic conditions. Similarly, a wild strain of brook charr in their natural streams near Sudbury, Ontario, failed to detect conspecific alarm cues in a weakly acidic stream (mean pH 6.11) while they responded to these cues in a neutral stream (mean pH of 6.88). This is the first demonstration that relatively small changes in ambient pH can influence alarm responses under natural conditions. These data suggest significant, sub-lethal effects of acid precipitation on natural waterways.

Assessment of Neutralization Ability of Soil for Acidic Precipitation

Acidic precipitation is a worldwide problem. Acids result from human activities, such as coal burning and the use of internal combustion engines. Though surface soils work to neutralize acidic precipitation and maintain land water at neutral levels, the environmental impact of acidic precipitation on the neutralization ability of soil has not been clarified. In this paper, the effects of acidic precipitation on the neutralization ability of the soil were experimentally examined in batch and column reactors with acidic solutions as the artificial acidic precipitation. Soil was collected in the Hokuriku area, located in the central part on the Japan-Sea side of Japan.On that coastal area, winter precipitation contains not only high amounts of acidic components, but also high concentrations of calcium and sodium ions derived from the sea. It was found from experimental results that calcium ions disturbed the neutralization ability of soil, but sodium ions did not. In this paper, the neutralization ability of soil was also assessed by a method based on the chemical equilibrium analysis of the relationship between the concentration of metal ions and pH values in the aqueous phase. The assessment suggested that calcium ions in precipitation prolonged the neutralization ability of soil.Carbon dioxide residing in small spaces in the soil was confirmed to enhance an increase in pH during the neutralization reaction. The existence of carbon dioxide was also found to promote the neutralization ability of soil. To elucidate the life-time neutralization ability of soil in respect of acidic precipitation, the effect of carbon dioxide residing in small spaces in soil cannot be neglected. This indicated that to achieve the aims of the present study, analyses of the solid, liquid and gas phases were required.

Effects of stream acidification and habitat on fish populations of a North American river

Water quality, physical habitat, and fisheries at sixteen reaches in the Neversink River Basin were studied during 1991‐95 to identify the effects of acidic precipitation on stream-water chemistry and on selected fish-species populations, and to test the hypothesis that the degree of stream acidification affected the spatial distribution of each fish-species population. Most sites on the East Branch Neversink were strongly to severely acidified, whereas most sites on the West Branch were minimally to moderately acidified. Mean density of fish populations ranged from 0 to 2.15 fish/m 2 ; biomass ranged from 0 to 17.5 g/m2. Where brook trout were present, their population density ranged from 0.04 to 1.09 fish/m 2

The cumulative effects of climate warming and other human stresses on Canadian freshwaters in the new millennium

Climate warming will adversely affect Canadian water quality and water quantity. The magnitude and timing of river flows and lake levels and water renewal times will change. In many regions, wetlands will disappear and water tables will decline. Habitats for cold stenothermic organisms will be reduced in small lakes. Warmer temperatures will affect fish migrations in some regions. Climate will interact with overexploitation, dams and diversions, habitat destruction, non-native species, and pollution to destroy native freshwater fisheries. Acute water problems in the United States and other parts of the world will threaten Canadian water security. Aquatic communities will be restructured as the result of changes to competition, changing life cycles of many organisms, and the invasions of many non-native species. Decreased water renewal will increase eutrophication and enhance many biogeochemical processes. In poorly buffered lakes and streams, climate warming will exacerbate the effects of acid precipitation. Decreases in dissolved organic carbon caused by climate warming and acidification will cause increased penetration of ultraviolet radiation in freshwaters. Increasing industrial agriculture and human populations will require more sophisticated and costly water and sewage treatment. Increased research and a national water strategy offer the only hope for preventing a freshwater crisis in Canada.

Sequential Effects of Acidic Precipitation and Drought on Photosynthesis and Chlorophyll Fluorescence Parameters of Pinus radiata D. Don Seedlings

Summary We studied the sequential effect of simulated acid rain (SAR) and water stress on net photosynthesis (A), internal CO 2 concentration ( Ci ), stomatal conductance (g), and instantaneous water use efficiency (A/E), and the photochemical damage caused by these stressors by analysing chlorophyll fluorescence parameters such as Fv/Fm, Fv/Fo and Fm/Fo. SAR caused inhibition of photosynthesis. The depletion of CO 2 assimilation seems not to be solely a stomatal effect as effects on chloroplasts contribute to this photosynthetic inhibition. No noticeable damage seems to occur to the photochemical apparatus since well-watered plants treated with acid rain did not show any change in the chlorophyll fluorescence. Water stress produced a large effect on both gas exchange and chlorophyll fluorescence parameters, indicating structural and functional damage. Interactions among SAR and drought had a larger impact on all parameters studied. However, after rewatering, significant recovery in both gas exchange and chlorophyll fluorescence parameters occurred within 6 days, although the values measured prior to the imposition of treatments were not recovered. We conclude that Pinus radiata exposed to acid rain were affected in a wide range of components in the photosynthetic apparatus, thereby modifying its response to sequential drought stress.

Structural and functional responses of benthic macroinvertebrates to acid precipitation in two forested headwater streams (Vosges Mountains, northeastern France)

From December 1996 to August 1997, beech litter breakdown and stream benthic macroinvertebrate communities were investigated to assess the effects of acidic precipitation on community structure and function in two second-order headwater streams of the Vosges Mountains (NE France). Because of microscale changes in bedrock mineral composition, one of the streams was acidified (mean pH=4.53, mean total Al=421 μg.l-1) and the other circum-neutral (mean pH=7.23, mean total Al=36 μg.l-1). Results showed that both litter breakdown rate and macroinvertebrate community structure were drastically affected under acidic conditions. The rate of leaf litter breakdown decreased by nine times in the acidic stream. Benthic sampling showed that scrapers were totally eradicated and both gathering and filtering collectors were drastically reduced. Such drastic effects appear to be the consequences of the toxicity of acid water including both proton and aluminum toxicity. A decrease in shredder abundance and a shift from the efficient acid-sensitive Amphipoda Gammarus fossarum to acid-tolerant Nemouroidea (mainly Leuctra sp.) was observed in the acidic stream. Our results indicate that freshwater acidification significantly alters the action of shredders processing leaf litter in the acidic stream. Consequently, interactions between structural and functional responses to acidification probably have profound consequences on the efficiency of acidified stream ecosystems, which in return may alter downstream functioning.

Sequential Effects of Acidic Precipitation and Drought on Water Relations of Pinus radiata Seedlings

In this work we investigated the sequential effects of simulated acid rain and drought on water relations of radiata pine ( Pinus radiata D. Don) seedlings. Whole seedlings were firstly subjected during 1 month to acid rain, pH 3.0, applied 5 times a week at 3 mm precipitation equivalent per day. Afterwards, drought treatment was applied by withholding water for 20 days and subsequent rewatering for 6 days to analyze the sequential effect of acid precipitation and drought. Water status parameters were determined before the initiation of acid rain treatment and within 3 weeks after the end of treatment. Acid rain treatment in well-watered plants did not affect either water potential or relative water content, whereas a marked effect on electrolyte leakage from the needles and on instantaneous transpiration was recorded. Drought treatment had great effects on leaf water potential (-2.5 MPa), RWC (50 % diminution), membrane permeability (340 % increase) and transpiration rate (25 % inhibition). Interactions involving acid precipitation and drought led to much greater impacts on all of the parameters analyzed. We conclude that although acid rain had slight, if any, direct effects on the water relations of well-watered radiata pine, it altered the drought tolerance of this tree species. Under conditions of soil-water deficit, plants exposed previously to acid rain are more sensitive to drought and desiccation.

Acid-rain monitoring in East Asia with a portable-type ion-exclusion–cation-exchange chromatographic analyzer

A monitoring system consisting of a portable-type conductimetric ion-exclusion–cation-exchange chromatographic (CEC) analyzer and a meteorological satellite data analyzer has been investigated for the evaluation of the effects of acid precipitation on natural and urban environments in East Asia. The portable ion-exclusion–CEC analyzer uses a polymethacrylate-based weakly acidic cation-exchange resin column in the H +-form and a weak-acid eluent (tartaric acid–methanol–water) and is applied for the simultaneous determination of anions (SO 4 2−, NO 3 −, and Cl −) and cations (Na +, NH 4 +, K +, Mg 2+, and Ca 2+) in precipitation transported from mainland China to central Japan, as mapped by the meteorological satellite data analyzer. Linear calibration graphs of peak area versus concentration for anions and cations were observed in the concentration range 0–1.0 m M for the anions and 0–0.5 m M for the cations. Detection limits at a signal-to-noise ratio of 3 were in the range 5.18–12.1 ppb for the anions and 6.58–16.5 ppb for the cations. The practical utility of this monitoring system is presented.

Environmental advocacy, the Adirondacks and air quality

This paper is intended to clarify and document the role environmental advocacy has played in helping to motivate Congress, the Administration, and the Environmental Protection Agency to adequately address the devastating effects of acid precipitation on forested and aquatic ecosystems of the Adirondack Park and other sensitive receptor areas. It details and emphasizes the failure of the Clean Air Act Amendments of 1990, particularly the Acid Rain Provisions, to solve the acid rain problem, which still continues. Also detailed is the reluctance of policy makers and enforcers and regulators to take the additional steps necessary to protect the nation's most sensitive ecosystems from the ravage of acid rain. The basic steps that need to be taken, particularly by Congress, are identified. Recognition is paid to several of the scientists/researchers/academicians, as well as policy makers, who have, along with the advocates, caused the progress made to date, and helped set the agenda for the final resolution of acid rain.

Acid Rain and Natural Organic Matter (NOM)

Twentyfive years of research on the effects of acid rain on rivers and lakes has, to a very small extent, documented changes in the nature and properties of natural organic matter (NOM). In Western Norway, a "whole-watershed-artificial-acidification-experiment" took place in the period 1988–1996. The goals of this long-term experiment were to study the role of NOM in acidification of surface water and the effects of acid precipitation on the quality and properties of NOM. In the HUMEX project (Humic Lake Acidification Experiment) one half of a lake and the corresponding catchment was artificially acidified with H2SO4 and NH4NO3 over a period of 5 years. The other half of the lake and catchment served as a control. In addition to monitoring of the general chemical composition of the water from the two lake halves, a number of other chemical and biological characteristics were studied. Here, we report the results related to changes in the nature and chemical properties of NOM. During the first few years of acidification, a significantly lower concentration of NOM was recorded in the acidified half of the catchment, compared with the control. However, statistical analyses of all data (covering a 2-years pre-treatment period and 5 years of treatment) related to the concentration of NOM (TOC, colour, and UV absorbance) did not suggest any significant effect on the quantity of NOM. This apparent discrepancy between the initial decrease in the concentration of NOM and no effect when the whole 5-years period is considered, may be due to the results of two different simultaneous processes. The results suggest that there first was a reduction of TOC and colour, as a consequence of the acidification, followed by an increase, perhaps owing to increased fertilisation (nitrogen) and in addition to a general temperature increase during the period. In addition, short-term studies of the aquatic surface microlayers, lipophilicity of the NOM, content of organic sulfur, and molecular size indicate differences in the quality of the NOM between the two lake halves, which could affect light absorption. Saurer Regen und natürliche organische Wasserinhaltsstoffe In 25 Jahren Forschung zu den Auswirkungen des sauren Regens auf Flüsse und Seen wurden in geringem Ausmaß Veränderungen von Natur und Eigenschaften natürlicher organischer Wasserinhaltsstoffe (natural organic matter – NOM) dokumentiert. In Westnorwegen fand von 1988 bis 1996 ein Großversuch statt, in dem ein ganzes Wassereinzugsgebiet einer künstlichen Versauerung unterzogen wurde (whole watershed artificial acidification experiment). In diesem Langzeitexperiment sollten die Rolle der NOM bei der Versauerung von Oberflächenwasser und die Auswirkungen saurer Niederschläge auf Qualität und Eigenschaften der NOM untersucht werden. Im Rahmen des Projektes HUMEX (humic lake acidification experiment – künstliche Versauerung eines huminstoffreichen Sees) wurde ein See durch eine Absperrung in zwei Hälften unterteilt. In der einen Hälfte des Sees wurde über einen Zeitraum von 5 Jahren künstlich eine Versauerung herbeigeführt, indem die Wasserfläche und das umliegende Einzugsgebiet mit H2SO4 und NH4NO3-Lösung beregnet wurden. Die andere Hälfte des Sees mit ihrem Einzugsgebiet diente als unbeeinflußte Kontrolle. In dieser Zeit wurden die chemische Zusammensetzung des Wassers in den beiden Seehälften sowie eine Reihe weiterer chemischer und biologischer Meßgrößen verfolgt. In den ersten Jahren wurde in der versauerten Hälfte des Sees eine im Vergleich zur Kontrolle signifikant niedrigere Konzentration natürlicher organischer Wasserinhaltsstoffe gefunden. Über den gesamten Zeitraum jedoch – 2 Jahre Beobachtungszeit vor der künstlichen Versauerung und 5 Jahre Säureeintrag – ergab die statistische Analyse aller Daten zur Konzentration der NOM (gesamter organisch gebundener Kohlenstoff (TOC), Färbung und UV-Absorbanz) keinen Hinweis auf eine signifikante Beeinflussung der natürlichen organischen Wasserinhaltsstoffe bezüglich ihrer Quantität. Diese Diskrepanz zwischen der anfänglichen Abnahme der NOM-Konzentration und der bei Betrachtung des gesamten Versuchszeitraums beobachteten Konstanz konnte auf zwei unterschiedliche, gegenläufige Prozesse zurückzuführen sein: Zunächst nehmen TOC-Konzentration und Färbung als Folge der Versauerung ab, dann erfolgt eine NOM-Zunahme aufgrund des gestiegenen Nährstoffgehalts (Stickstoff). Zu berücksichtigen ist dabei auch, daß während des Versuchszeitraums ein Temperaturanstieg beobachtet wurde. Zusätzlich zur Langzeitbeobachtung grundlegender Parameter wurden einzelne Untersuchungen zu Lipophilie der NOM, Gehalt an organisch gebundenem Schwefel und Molekülgröße.

The Effects of Acid Precipitation and Ozone on the Ectomycorrhizae of Red Spruce Saplings

The effects of acid precipitation and ozone on the composition of the ectomycorrhizal community of red spruce saplings were evaluated. In 1986, saplings were excavated from a site in Maine that had been clear-cut in 1979. Saplings were then potted in native soil and transported to Ithaca, New York. With the exception of an ambient control treatment, trees were grown in open-top chambers. Saplings were exposed to five levels of ozone and three levels of acid precipitation beginning in July 1987. Ectomycorrhizae were sampled in 1988 and 1991 after one and four years of treatment, respectively. Although the percentage of root tips infected by ectomycorrhizal fungi was not affected by treatments, a shift in the composition of the ectomycorrhizal community occurred in response to acid precipitation treatments for both sampling years. Among the seven ectomycorrhizal morphotypes identified, the percent composition of one morphotype increased and another decreased in response to higher rain acidity. Alone, ozone treatments did not influence ectomycorrhizal composition; however, a significant interactive response to ozone and acid precipitation was observed in the organic soil horizon in 1988. Such shifts in the composition of the ectomycorrhizal community may indicate that the experimental trees were stressed by pollution treatments.

The effect of acid irrigation on enzyme activities of the single partners of ectomycorrhizas from a limed stand of Norway spruce (Picea abies [L.] Karst.)

The aim of our investigations was to elucidate the effects of acid precipitation on some enzymes of the primary metabolism of ectomycorrhizas. Mycorrhizas of the type of Piceirhiza nigra Gronbach and of Russula ochroleuca (Pers.) Fr. and Tuber puberulum Berk. and Br. were collected from a stand of Norway spruce (Picea abies [L.] Karst.) during the growing seasons of 1991 and 1992. The experimental plots had been limed (Ca: 22 kmol ha-1, Mg: 20 kmol ha-1) in 1984 and exposed to acid irrigation (pH 2.7–2.8, H2SO4: 2 kmol ha-1 a-1) from 1984 to 1990. Crude extracts of mycorrhizas were assayed for the activities of glucose-6-phosphate dehydrogenase (G6P-DH, EC 1.1.1.49), 6-phosphogluconate dehydrogenase (EC 1.1.1.44), NADP-dependent isocitrate dehydrogenase (EC 1.1.1.42) and NAD-dependent glutamate dehydrogenase (EC 1.4.1.2). The influence of the experimental treatments on these enzyme activities of the primary metabolism was generally low. For P. nigra, the activity of G6P-DH was decreased on the irrigated plot (photometric determinations). This seems to be a selective effect on the fungal partner, since quantitative enzyme electrophoresis revealed a decrease in the percentage of the fungal enzyme activity in relation to the total enzyme activity, whereas the content of the fungal compound ergosterol was not affected. A decrease in the fungal G6P-DH activity could also be detected in mycorrhizas of Tuber puberulum. There was also a seasonal variation in the proportion of fungal activity of G6P-DH in relation to the total G6P-DH activity. In the photometric assay (total activity) the effect was not discernible. This is indicative of a degree of regulation between the two partners, which could only be detected by quantitative enzyme electrophoresis. In addition, it could be deduced from the electrophoretograms, that in the case of G6P-DH and 6PG-DH the fungal enzyme activity was dominating in all mycorrhizas studied whereas in the case of ICA-DH the fungal band varied from being conspicuous to absent in different species of mycorrhizas. The banding pattern of G6P-DH was reproducibly different for all investigated species of mycorrhizas.

Effects of Acidic Precipitation and Ectomycorrhizal Inoculation on Growth, Mineral Nutrition, and Xylem Water Potential of Juvenile Loblolly Pine and White Oak

Individual and interactive effects of simulated acidic rainfall and mycorrhizal inoculation on growth and nutrient and water relations of loblolly pine (Pinus taedaL.) and white oak (Quercus albaL.) grown in a loam soil were examined. Seedlings of each species inoculated with basidiospores of the ectomycorrhizal fungus Pisolithus tinctorius(Pers.) Coker and Couch, a known my-cobiont of both loblolly pine and white oak, and uninoculated control seedlings received two simulated rains per week of either pH 3.6, 4.2, or 4.8 for 26 weeks. Higher acidity rainfall reduced the growth but increased mycorrhizal colonization of loblolly pine, while both loblolly pine and white oak exposed to these rains exhibited greater foliar injury. Inoculation with P. tinctoriusincreased growth and reduced foliar injury of both species. Foliar concentrations of P, S, and Cu in loblolly pine and white oak, Ca in loblolly pine, and Fe and Zn in white oak decreased with increasing rain acidity while the Al concentration of both species increased. Higher rainfall acidity also reduced soil pH and Ca and Mg concentrations while increasing soil AI. Foliage of inoculated seedlings of both species had higher N and P concentrations and lower Al concentrations than control seedlings. Following the final rain applications, a drought cycle was simulated by withholding irrigation for two weeks during which seedling xylem pressure potential and soil water potential were measured. One day after cessation of irrigation, xylem pressure potential of loblolly pine that had received pH 3.6 rains was lower than that of other treatments. Thereafter, xylem pressure potential and soil water potential of the inoculated treatment decreased below those of the control treatment in both species. These results suggest that acid deposition is detrimental to juvenile loblolly pine and white oak, but the magnitude of this effect is less than the positive response to ectomycorrhizal inoculation.